Up to now, a technique in which an acceleration sensor is buried in a back surface of a tire tread, and a road surface condition, for example, a condition of an asphalt road, a snowy road, or an frozen road, is estimated based on a detection signal of the acceleration sensor has been proposed (for example, refer to Patent Literature 1). Specifically, in the case where the acceleration sensor is buried in the back surface of the tire tread, when a portion of the tire tread corresponding to a placement location in which the acceleration sensor is disposed contacts a road surface in association with the rotation of the tire, a vibration component corresponding to the road surface condition is superimposed on a detection signal of the acceleration sensor. For that reason, up to now, a frequency component of the vibration in a ground contact section where the portion of the tire tread corresponding to the placement location of the acceleration sensor contacts the road surface is analyzed to estimate the road surface condition.